A known image reading apparatus includes a main unit and an openable unit which is configured to open and close a top surface of the main unit, which functions as a document receiving surface on which a document is placed. The openable unit includes a document tray on which a document is placed, a feeder that feeds the document along a feed path, and a reading portion which is disposed facing the feed path and configured to read an image of the document passing through the feed path. The main unit includes a main unit-side reading portion which is configured to read an image of a document placed on the document receiving surface, and a control circuit board which is configured to perform controls based on output signals of the reading portion and/or output signals of the main unit-side reading portion. A cable that transmits the output signals of the reading portion to the control circuit board is routed on the rear sides of the main unit and the openable unit. Additionally, a cable that transmits the output signals of the main unit-side reading portion to the control circuit board is routed inside the main unit to connect a CCD image sensor and a CCD circuit board to the control circuit board.
Generally, in the image reading apparatus, the feeder, the reading portion, and the main unit-side reading portion operate under control of the control circuit board, and an image reading process that reads an image of a document passing the feed path is performed.
In the image reading apparatus, a thick cable is used to transmit the output signals of the reading portion of the openable unit to the control circuit board of the main unit. However, the cable has been recently substituted for a flexible flat cable of which a plurality of coated wires are united to form a flat shape. In addition, a flexible flat cable has been also used to transmit the output signals of the main unit-side reading portion to the control circuit board.
However, the flexible flat cables as described above are likely to sustain noise. If the flexible flat cable is left without countermeasures taken to prevent noise, noise may occur in a signal to be transmitted by the flexible flat cable, and thus irregularity in image data for a document may occur in an image reading process.